A lot is known about the effectiveness of peer assisted learning and peer tutoring. In contrast, process-oriented research remains relatively limited. Since different kinds of interactions promote different kinds oflearning (King, 1997), it is important to understand exactly how peer tutors tutor and how their adopted strategies affect the learning opportunities generated within these learning environments. The need to disentangle peer tutors behavioural repertoire and its implications for students learning, experiences and the dynamics of the peer tutored learning environment raises as one considers that inexperienced or unskilled tutors, such as peers, have become the norm in tutoring settings nowadays. However, as peer tutors knowledge is often implicit, fragmented and poorly organised (Roscoe & Chi, 2007), and as it is known that they face the challenge of a double student-and-tutor role (Colvin, 2007), one can question whether and how peer tutors contribute to students learning. These reflections have stimulated this doctoral research project.In particular, this doctoral research project consisted of two empirical research phases. In a first phase (chapter 1), the behavioural strategies of peer tutors were investigated in-depth by means of a qualitative case study. Results showed that peer tutors engaged mainly in directive strategies, i.e.providing cut-and-dried answers or elaborations. Theseelaborations were, however, of a profound quality. In contrast, facilitative strategies (i.e.questioning, prompting or hinting) were less observed. What is more, they appeared to be rather general in nature. Furthermore, a typology of approaches to peer tutoring resulted from this study, i.e. motivational organisers, informers and questioners. Finally, it was shown that different types of peer tutors experienced tutoring differently.The second phase, represented by four empirical studies (chapters 2-5),built further on the results obtained in the first research phase. It aimed to investigate the effects of two different approaches to peer tutoring on students learning and experiences, as well to grasp the dynamics that resulted from both tutoring approaches in terms of students learning (inter-)actions adopted within the learning environment. For these purposes, a large-scale quasi-experimental study was set up in which two specific approaches to peer tutoring were induced, i.e. adirective versus facilitative approach. Chapter 2 and 3focused on the effects of these approaches to tutoring on students knowledge, understanding and actual skill performance. Chapter 2 revealed that while no maineffect of the approach to tutoring was found on students development of knowledge and understanding, nor on their actual skill performance, aninteraction effect existed between the approach to tutoring and students course-specific prior knowledge. More specifically, less knowledgeable students scored better in terms of their knowledge and understanding when being tutored by a facilitative peer tutor, while the opposite was true for high-knowledgeable students. Chapter 3 investigated this interaction effect more in-depth by means of extreme course-specific prior knowledge groups. These results nuanced the findings of chapter 2 as it appeared that the approach to peer tutoring only mattered for students who started the course with no or limited course-specific prior knowledge. The facilitative approach to tutoring remained to be most favourable. Chapter 4 focused on the learning (inter-)actions that were stimulated in students within both tutored learning environments. The main findings indicated that students tutored by a directive peer tutor uttered more non-elaborative comments or ignored peer tutors support. Also more informal actions and questions requesting confirmation or assessment-related information were observed. In contrast, facilitatively tutored students engaged mainly in elaborative actions, which were of a profound quality. However, this latter student group appeared to lack clarity as they mainly asked clarification questions. Questions requesting confirmation or assessment-related information occurred less than expected in this group. Finally, chapter 2 and 5 aimed to shed light on students perceptions and experiences within both tutored learning environments. It was shown thatdirectively tutored studenst appraised their tutored learning environment to a larger extent. Moreover directively tutored students' dislikes related mainly to peer tutors' expertise and organisational features. In contrast, facilitatively tutored students' dislikes concerned the perceived lack of clarity that resulted from peer tutors' approach to tutoring. Nevertheless, these students acknowledged more deep-level learning as a result of their attendance at these specifically tutored sessions.11.0pt;line-height:115%;font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language:AR-SA"lang="EN-GB">EN-GB" lang="EN-GB">